Found this page on making a generator from a lawnmower. Just thought I'd pass it on. http://www.theepicenter.com//tow082099.html
Few comments. Almost all of these make a generator from a ****** are dc generators to charge a battery. Except for the very expensive generators that allow the frequency to stay the same with changing RPM, they all require the motor to not only run at a fixed RPM, but to stay at the RPM under changing loads. That requires a better system than most small lawn mowers have. Then almost all modern push mowers use a system that requires you to hold a bail down and releasing it kills the engine and puts on a brake. They are also optimized to start with no real load as the blade is in effect a fan until you push it into the grass and it starts to cut. Last and not least, many of the cheaper motors are designed for a very short life and short run times. That said they are usually free, it is fun to do, and they do put out quite a bit of power. But a good Honda GX series engine from a water pump, air compressor, old generator, pressure washer etc is designed to operate under varying loads, has a design life of 4,000 hours instead of 500 to 1,000, has a larger gas tank and will run 8 hours a day for years. Guess you know what I play with.
here is a cheap welder that is almost the same set of parts used to build. I thought that a riding lawn more with a bad deck would be a good welder/generator that you could ride to the job site on the farm. http://www.motherearthnews.com/Alternative-Energy/1980-11-01/Build-a-20-Portable-DC-Arc-Welder.aspx kychas